Colour Blind Testing
It is estimated that eight per cent of males and fewer than 1 per cent (about 1 in 200) of females are colour deficient.
Most people suffering from colour blindness are born with the condition. They inherit the condition from their parents as an ‘X-linked trait’. This means that the gene causing the condition is located on the X sex chromosome. Males have an X and a Y sex chromosome, while females have a pair of X sex chromosomes.
What does that mean?
males are predominantly affected.
females are not predominantly affected but can be carriers of defective genes. Carriers carry the gene and can pass it on to half of their sons. Half of their daughters can be carriers. Carriers themselves are not affected by the defect.
if the father is colour-blind, all his daughters will be female carriers of defective genes. His sons will be spared unless the mother also carries the defective gene.
if the mother is colour-blind, all her sons will be affected and all her daughters will be female carriers.
Green colour weakness or blindness is the most common. Not all cases of colour blindness are congenital. Some diseases are acquired later in life, like diabetic eye disease, glaucoma, and retinal or optic nerve disease which may also disrupt colour vision.
Ishihara Colour Blind Test
The red-green colourblind test, i.e, the Ishihara test is a test for colour blindness or colour vision deficiency. Colour vision testing is done for those who cannot perceive the full range of the colour spectrum, cannot differentiate between colours, or cannot see colours vividly. The most common type of colour blindness is red-green, although some people are also colour blind to shades of blue and yellow, and, in rare cases, a person can be completely colour-blind, seeing the world in shades of grey. To determine the severity and causes of colour blindness, an optometrist at For Eyes can administer colour vision testing.
How Is a Colour-Blind Test Done?
The optometrists at For Eyes will conduct the colour-blind testing in a well-lit room. They will then present you with a series of test cards that have multiple dots on each. These cards will have patterns, letters, or numbers that will be perceived by those who can see the whole colour spectrum, but those who have a colour vision impairment may struggle to see the symbols among the dots. More advanced colour vision tests can be conducted such as a colour lantern test.
We can help you determine the severity and cause of your colour blindness. Book an eye exam today.